Recently, music projects that in former times would have required an array of professional studio equipment can now be completed in a home or project studio, using a personal computer and readily available resources. A personal computer that executes digital audio studio software such as e.g. Logic Pro 7 of Apple Computer Inc. can serve as a work-station for recording, arranging, mixing, and producing complete music projects, which can be played back on the computer, burned on a CD or DVD, or distributed over the Internet. Such audio studio software also allows to record, generate, process and output audio in surround audio formats, such as e.g. 5.1 or 7.1 surround formats, having 5 or 7 audio channels as well as optionally also an additional low frequency effects LFE channel.
Such audio studio software is also often used by musicians, professional or hobbyists, to improve studio recordings by simulating real-world spaces such as e.g. a cathedral, an opera house, or a music stage. This is often performed by using a so-called convolution reverb effect, wherein a single impulse response or a set of impulse responses of such a desired location is used. These impulse responses are also sometimes referred to as acoustic fingerprint of the location. In performing the convolution reverb effect, each channel of e.g. a surround audio track is convoluted by a corresponding impulse response, each impulse response of the set of impulse responses of the desired location to be simulated having a same length in time, respectively a same number of samples in case of the impulse responses being provided as digital sample data, e.g. of 44.1 kHz or 96 kHz sampling rate, each sample corresponding to e.g. 16 bit or 24 bit. Overall, such processing results in a number of convolution processing operations that corresponds to the number of channels in the surround audio track that are subjected to convolution reverb processing. However, such processing does not take into account that also the reverberations of the location that may be audibly perceived in one channel, but are caused by, respectively originate from an audio signal in another channel contribute to the overall spatial localisation and “spaciousness” of the resulting perception.
Recently, there have also been developed systems that offer a “true surround” convolution reverb effect, wherein each reverberated output audio channel signal respectively is the sum of each inputted audio channel signal convoluted by a corresponding impulse response. In comparison, this provides for an audio convolution reverb effect that allows for a perceivably much better simulation of an existing space, however requires a number of convolution processing operations that corresponds to the square of the number of channels in the surround audio track that are subjected to convolution reverb processing in case the number of input channels is the same as the number of output channels. Otherwise the number of required convolution processing operations corresponds to the product of the number of input channels times the number of output channels. Therefore, it will be understood by those skilled in the art that such a “true surround” convolution reverb requires a number of computations that is comparably much increased. As a result, even with recent increases in processor speed, currently available personal computers cannot perform such “true surround” convolution reverb in real-time. Instead, such effects have to be processed “off-line”, requiring processing time which is usually far longer than the time of the actual surround audio file to be processed.